As part of an expansion, Interstate 10 will get lanes reserved for transit and other high-occupancy vehicles, a design that planners hope to duplicate on other highways in San Antonio.

At its meeting Monday, the Alamo Area Metropolitan Planning Organization approved a plan to widen I-10 north of Loop 1604 by adding two lanes in each direction between La Cantera Parkway and Ralph Fair Road, likely by 2019. One lane will be for high-occupancy vehicles, such as buses and carpools, and the other for all vehicles to use.

The vote ended a somewhat contentious debate that started in December, when the Texas Department of Transportation introduced the HOV idea to replace a plan to add toll lanes and direct connectors on that part of I-10. The plan is similar to one to convert the part of U.S. 281 between Loop 1604 and Borgfeld Drive into a six-lane freeway with two HOV lanes, the first ones approved in the San Antonio area.

U.S. 281 and I-10 might pave the way for HOV lanes on other busy corridors. The MPO is studying the feasibility of adding them to highways now slated for tolled expansions, including Interstate 35 and Loop 1604.

“These work really well in a system, so I think we have work to do to see how these HOV lanes can continue into downtown,” said Mario Jorge, San Antonio district engineer for TxDOT.

As the MPO considered the nontoll I-10 plan, several of its board members questioned whether the HOV lanes would provide the most efficient means of relieving congestion in a heavily traveled area. Don Dixon, a retired engineer, echoed those concerns Monday.

“There needs to be added capacity on that highway, no question about it,” he said. “If you have four lanes in each direction and those cars move freely on those four lanes, you’re going to have a much better system than having restricted lanes.”

Earlier this year, the MPO brought in two experts to explain how such lanes have performed in other cities in Texas and the nation. Dallas and Houston, two of many cities that have adopted HOV lanes, incorporated them into their highway networks years ago.

Ginger Goodin, senior research engineer for the Texas Transportation Institute, presented a list of criteria that can help determine how well an HOV lane will perform. Typically, the highway would have an average daily traffic count of 25,000 cars per lane, an average speed of 30 mph or less during peak travel times and high levels of transit and carpool use, among other things.

I-10 traffic hasn’t hit that mark yet: In 2014, about 87,500 cars traveled the highway each day in the four lanes near Ralph Fair Road, and that number increased to about 123,350 in the six lanes near La Cantera. On a daily basis, that works out to 21,875 and 20,558 cars per lane, respectively.

If the highway is expanded to have three general-purpose lanes, the section near La Cantera would reach 25,000 cars per lane in 2023, MPO traffic projections show. The section near Ralph Fair Road would reach that point in 2037.

Jeff Haberstroh, a Boerne city councilman and MPO board member, emphasized that the MPO should keep tabs on traffic once the HOV lanes open and turn them into general-purpose lanes if necessary.

“We’ve discussed having a possible turn-back, should these lanes be underutilized,” he said. “We need to be able to manage traffic congestion in the future.”

The Texas Transportation Commission, TxDOT’s governing body, will vote on whether to modify the project to include the HOV lanes. If it approves the changes, as expected, TxDOT will partner with VIA Metropolitan Transit to determine whether the lanes should have HOV restrictions only during peak hours and whether vehicles would need two or three occupants to qualify, Jorge said.

The MPO could vote to lift the restrictions if the lanes underperform after several years of use. Jorge said that will depend, to some degree, on whether similar lanes are built in other areas.

“The challenge is how to create a system or network of HOV lanes,” he said. “If they’re left in isolation for some time, I think we’ll have to look at them again.”kblunt@express-news.net